1. Field of the Invention
The present invention relates to a diode laser excitation solid-state laser amplifier and a diode laser excitation solid-state laser, particularly to the excitation section of the laser.
2. Description of the Related Art
FIG. 28 is a block diagram of an excitation module used for a conventional diode laser excitation solid-state laser amplifier shown in, for example, the document "Solid-State Laser Engineering, Springer-Verlag, p. 348". In FIG. 28, two diode laser arrays 3 are fixed to one side of a trigonal-prismatic heat sink 5 by turning its light emitting section 4 to the left of FIG. 28. Moreover, a cylindrical lens 34 for condensing the excitation light emitted from the diode laser arrays 3 is fixed to the heat sink 5 adjacently to the light emitting section 4 of the diode laser arrays 3. An electric cooler 301 for adjusting the temperature of the heat sink 5 is set to the side opposite to the light emitting section 4 of the diode laser arrays 3 of the heat sink 5. Moreover, at the outside of the cooler 301, a heat exchanger 302 for removing heat from the diode laser arrays 3 through the heat sink 5 and the electric cooler 301, is set adjacently to the electric cooler 301.
Cooling water circulates through the heat exchanger 302 to exchange heat with the diode laser arrays 3 through the heat sink 5. The electric cooler 301 is set between the heat exchanger 302 and the heat sink 5 so as to be sandwiched by them. Therefore, by cooling the heat sink 5 by the electric cooler 301, it is possible to quickly adjust the temperature of the diode laser arrays 3 without changing the temperature of the cooling water to be circulated through the heat exchanger 302.
Two diode laser arrays 3 are fixed to the heat sink 5 in the same direction. The cylindrical lens 34 is fixed to the front of the light emitting section 4 of the diode laser arrays 3 and the excitation light emitted from the light emitting section 4 is condensed by the cylindrical lens 34. Moreover, the electric cooler 301 is set between the heat sink 5 and the heat exchanger 302 so as to be sandwiched by them. Therefore, it is possible to adjust the wavelength of the excitation light emitted from the diode laser arrays 3 by adjusting the temperature of the heat sink 5 with the electric cooler 301. An excitation module 90 comprises such components as the heat sink 5, diode laser arrays 3, cylindrical lens 34, electric cooler 301, and heat exchanger 302.
FIG. 29 is a perspective view showing a state in which the excitation module 90 having the structure in FIG. 28 is fixed to a support plate 303 together with the solid-state laser rod 1 and a flow tube 2. In the case of the above structure, four excitation modules 90 are set to one solid-state laser rod 1 around the rod 1. Moreover, each excitation module 90 is set by the fact that an end face of the heat sink 5 is fixed to the support plate 303 and one end of the module 90 is supported. Furthermore, each light emitting section 4 of the diode laser array pair 3 fixed to each of four excitation modules 90 is turned toward the solid-state laser rod 1 and the excitation light emitted from the light emitting section 4 receives an action so that a condensed line is produced in the cross section of the solid-state laser rod 1 by the cylindrical lens 34. Therefore, the flow tube 2 is provided around the solid-state laser rod 1 and a cooling medium is flown to a space formed between the solid-state laser rod 1 and the flow tube 2 to cool the solid-state laser rod 1.
Because a conventional diode laser excitation solid-state laser amplifier and a diode laser excitation solid-state laser using the amplifier are constituted as described above, a problem occurs that only one excitation light applying direction is obtained from one excitation module. Therefore, a problem occurs that, to obtain uniform excitation distribution in the solid-state laser rod 1, a plurality of excitation modules corresponding to the number of applying directions must be prepared to emit excitation light from a plurality of directions.
Moreover, to increase the output of a diode laser excitation solid-state laser, the number of diode laser arrays 3 set to excitation modules is increased. Therefore, the length of the heat sink 5 must be increased along the solid-state laser rod 1. Furthermore, to obtain a uniform excitation distribution in the longitudinal direction of the solid-state laser rod 1, it is necessary to keep the interval between every diode laser array 3 and the solid-state laser rod 1 constant. Therefore, a problem occurs that a higher manufacturing accuracy is required and fabrication of the excitation module 90 as a laser is further increased in size.
Furthermore, because an excitation module is supported at only one end, problems occur that the distances between the diode laser array 3 and the solid-state laser rod 1 are easily changed and it is difficult to keep stable amplification characteristic and laser output. Furthermore, because the uniformity of the excitation distribution in the solid-state laser rod 1 is also deteriorated, a problem occurs that the quality of laser beam is also deteriorated.